The anti‐androgen hydroxyflutamide and androgens inhibit interleukin‐6 production by an androgen‐responsive human osteoblastic cell line

LC Hofbauer, RM Ten, S Khosla - Journal of Bone and Mineral …, 1999 - academic.oup.com
LC Hofbauer, RM Ten, S Khosla
Journal of Bone and Mineral Research, 1999academic.oup.com
While androgens clearly have significant skeletal effects, the paracrine mediators of
androgen action on bone are at present unclear. Interleukin‐6 (IL‐6) is a candidate cytokine
that is produced by osteoblastic lineage cells and promotes osteoclastogenesis and bone
resorption. Here, we assessed constitutive as well as IL‐1β–and tumor necrosis factor‐α
(TNF‐α)–stimulated IL‐6 mRNA expression by Northern analysis and protein secretion by
immunoassay in a human androgen‐responsive osteoblastic cell line (hFOB/AR‐6) which …
Abstract
While androgens clearly have significant skeletal effects, the paracrine mediators of androgen action on bone are at present unclear. Interleukin‐6 (IL‐6) is a candidate cytokine that is produced by osteoblastic lineage cells and promotes osteoclastogenesis and bone resorption. Here, we assessed constitutive as well as IL‐1β– and tumor necrosis factor‐α (TNF‐α)–stimulated IL‐6 mRNA expression by Northern analysis and protein secretion by immunoassay in a human androgen‐responsive osteoblastic cell line (hFOB/AR‐6) which contains ∼4000 androgen receptors (ARs)/nucleus. Treatment with 5α‐dihydrotestosterone (DHT) dose‐dependently inhibited constitutive and TNF‐α/IL‐1β–stimulated IL‐6 mRNA steady‐state levels in hFOB/AR‐6 cells by 70–80% at 10−7 M. In addition, testosterone also suppressed TNF‐α/IL‐1β–stimulated IL‐6 mRNA levels by 57%, while the adrenal androgen dehydroepiandrosterone had no effect. Of note, the specific AR antagonist, hydroxyflutamide, also inhibited IL‐6 mRNA levels by 70%. Consistent with the Northern analyses, treatment with 5α‐DHT, testosterone, and hydroxyflutamide also inhibited IL‐6 protein production by 79%, 62%, and 71%, respectively (p < 0.001), while these agents had no effect on IL‐6 soluble receptor levels. Finally, we demonstrated that hydroxyflutamide treatment of hFOB/AR‐6 cells markedly inhibited the activation and binding of NF‐κB (a known stimulator of IL‐6 gene transcription) to its response element, thus providing a potential mechanism for its effect on IL‐6 production by osteoblasts. These data are consistent with the hypothesis that suppression of osteoblast IL‐6 production by androgens may mediate, at least in part, the antiresorptive effects of androgens on bone. Moreover, our findings also indicate that hydroxyflutamide, which is a known AR antagonist in most tissues, may function as a selective AR modulator for effects on IL‐6 production by osteoblasts.
Oxford University Press